Friday, November 14, 2014

After Mowing Spray Activity

I’ve added a new species to my list of woodies that readily colonize an open field.  Persimmon, Diospyros virginiana, has aggressively infiltrated the field, growing with such vigor that it has produced fruit in just five years time.  That fruit is full of large seeds ready to claim their place in the field. 

These Persimmons were the only woody species that grew so large in five years that I chose not to run them over with the mower.  The mower would have taken it, but the blade gets worn enough on small stems.  There are a very few mature Persimmon trees scattered about the property, but none are especially close to this part of the field.  I suppose some animal stuffed with Persimmon fruit spent a relaxing time here in the corner of the field and dropped the seeds around.

Most of the woody plants were small and easy to handle.  There were several dozen young Multiflora Rose plants, some with multiple stems radiating from a central root.  The mower shortened the stems, but the plant still needs to be trimmed down in order for the herbicide spray to be effective.

By sliding my loppers in beneath the stems, I can cut the rose at ground level where the plant is concentrated into a single trunk.  Glyphosate is easily applied to the single cut and will effectively kill the plant.

Yucca filamentosa is beginning to show some aggressive invasive tendencies.  The basis for the name is easy to see from the fibrous filaments exposed atop the shredded leaves.  These plants are obviously growing from seed, but Yucca plants have just a single pollination agent in the form of a Yucca Moth.  Without the moth, the plant is not pollinated and no seed results.  I have been looking for 25 years to see a Yucca Moth visiting the Yucca flowers and have yet to find one.  Apparently I’ll have to try even harder.

At first glance the Yucca basal rosette appears to represent a single plant.  Actually, the clump is composed of numerous plants and slowly spreads to occupy more and more space.

Each stump gets a little squirt of glyphosate.  This is my first year treating Yucca stumps in this manner, so I’ll have to wait until next spring to see if the plant is completely killed.

The mower blade shatters the stumps of most woody plants.  Spraying herbicide on a stump in this condition is usually ineffective.  Those splayed ends will die from dehydration and the glyphosate will not move into the living tissue.

More likely, the stump will sprout new stems at ground level.  This Ash stump looks to have been cut off and left untreated when the field was mowed five years ago.  The most effective way to eliminate this tree is to cut below the sprouts and apply herbicide.

I settled on November 1 as the beginning of my field mowing season because woody plant species seem particularly susceptible to a stump treatment of glyphosate at this time of year.  This treated Ash will not be growing again.  


  1. You are such a wealth of useful knowledge. Thank you. A question though - I looked back on earlier posts under "Spraying Shrubs" and one on "Glyphosate" and didn't pick on the formulation of glyphosate you use. Do you prepare your own from concentrate or simply buy a pre-mix from the garden store? Also, I noticed that your technique seems to have changed from cutting, allowing re-sprouts and spraying the new growth to cutting the stump flush with the ground and spraying the fresh cut. Is that b/c of the season in which you are treating or b/c spraying the freshly cut stump is more effective?

  2. Hi, Mel. For stump spraying I use the standard concentrate formulation which is 41 percent glyphosate. This concentration is necessary to get good success treating Autumn Olive and Walnut stumps. Most other species can be killed using a 20 percent solution and some others, such as Japanese Barberry, are susceptible to solutions as low as one percent glyphosate. My decision to use the standard concentrate on all species is primarily based on the time I have available for this activity. If I had a two chamber spray bottle that could be set for a specific herbicide concentration at each pull of the trigger, I could easily treat each stump with just the right amount of chemical. Carrying multiple spray bottles of different concentrations or mixing small batches of different dilutions in the field would just be too difficult and time consuming.

    I am always trying new management techniques. When I first began mowing the fields in the fall, marking woodies and spraying regrowth in the spring, I was marking an average of 250 plants per acre that required treatment. At that time, I did most of the mowing in December and sprayed in April or May with a 1.8 percent glyphosate solution. This method was quite effective, except for control of Autumn Olive and Black Walnut which were hard to kill with a foliar application. I also had trouble with species like Ash that grew quickly, but produced very little leaf area until they were two or three feet tall. It was hard to spray these without spraying much of the surrounding vegetation. I needed a new control method for these species.

    When I mowed this year, I marked an average of 20 plants per acre that needed to be cut and sprayed. This is more than a 90 percent reduction over what I was dealing with in the early years. I am also doing the mowing in November, because I noticed that the invasive non-native species still had green leaves at this time of year. This makes them easy to see and in an ideal condition to be killed by the herbicide. Stump treatment also makes it possible for me to go into tall grass stands in the fall and deal with woody plants in a situation where marking and relocating in the spring would be highly difficult. If I was dealing with fields in the same condition as when I first began mowing, I would use the fall cut and spring spray method to thin out the woodies, but I would mark the Autumn Olive differently and treat them to a stump application.